Melt-processable thermotropic polymers which are capable of forming an anisotropic melt phase constitute a recognized class of polymers which is well known in the art. The anisotropic character of the polymer melt may be confirmed by conventional polarized light techniques whereby crossed-polarizers are utilized. More specifically, the anisotropic (i.e., ordered) nature of the melt phase may conveniently be confirmed by the use of a Leitz polarizing microscope at a magnification of 40.times. with the sample on a Leitz hot stage and under a nitrogen atmosphere. The amount of light transmitted changes when the sample is forced to flow; however, the sample is optically anisotropic even in the static state. On the contrary typical melt-processable polymers do not transmit light to any substantial degree when examined under quiescent conditions and are isotropic in nature.
Following formation in an appropriate reaction zone, the melt-processable thermotropic polymers commonly are melt-extruded and are cut to pellet form with or without the presence of a solid particulate filler and/or reinforcing agent. The resulting polymer may be used to form fibers, films, three-dimensional molded articles, or three-dimensional melt-extruded articles. If the polymer pellets include substantial quantities of a solid particulate filler and/or reinforcing agent, then they tend to be used primarily for forming three-dimensional molded articles and/or three-dimensional melt-extruded articles rather than fibers, as will be apparent to those skilled in the art.
Heretofore, it has been observed that shaped articles formed from thermotropic polymers which are capable of forming an anisotropic melt phase commonly exhibit less than optimum surface characteristics following molding or melt-extrusion. For instance, upon careful examination small blisters or blemishes may be observed on the surface. Also, upon extended heat treatment to improve the strength thereof or usage of an article molded from the same at an elevated temperature (e.g., 200.degree. C.) the surface appearance of the article commonly will become even less uniform.
It is an object of the present invention to provide an improved process for producing pellets from a melt-processable thermotropic polymer which is capable of forming an anisotropic melt phase whereby the resulting pellets are capable of undergoing melt-processing to form shaped articles having improved physical properties.
It is an object of the present invention to provide an improved process for producing pellets from a melt-processable thermotropic polymer which is capable of forming an anisotropic melt phase whereby the resulting pellets are capable of undergoing melt-processing to form shaped articles that have an improved surface appearance.
It is an object of the present invention to provide an improved process for producing pellets from a melt-processable thermotropic polymer which is capable of forming an anisotropic melt phase whereby the resulting pellets are capable of undergoing melt-processing to form improved articles which can be heat-treated for an extended period of time to impart strength improvement while retaining improved surface characteristics.
It is an object of the present invention to provide an improved process for producing pellets from a melt-processable thermotropic polymer which is capable of forming an anisotropic melt phase whereby the resulting pellets are capable of undergoing melt-processing to form improved molded articles which can better withstand extended usage at an elevated temperature while retaining improved surface characteristics.
It is an object of the present invention to provide improved pellets comprising a melt-processable thermotropic polymer which is capable of forming an anisotropic melt phase which pellets can be melt-processed to form shaped articles having improved physical properties.
It is an object of the present invention to provide improved pellets comprising a melt-processable thermotropic polymer which is capable of forming an anisotropic melt phase which pellets can be melt-processed to form shaped articles having an improved surface appearance.
It is another object of the present invention to provide improved pellets comprising a melt-processable thermotropic polymer which is capable of forming an anisotropic melt phase which pellets can be melt-processed via injection-molding and/or melt-extrusion to form improved three-dimensional articles which can be heat-treated for an extended period of time to impart strength improvement while retaining improved surface characteristics.
It is a further object of the present invention to provide improved pellets comprising a melt-processable thermotropic polymer which is capable of forming an anisotropic melt phase which pellets can be melt-processed via injection-molding and/or melt-extrusion to form improved three-dimensional articles which can better withstand extended usage at an elevated temperature while retaining improved surface characteristics. These and other objects, as well as the scope, nature, and utilization of the claimed invention will be apparent to those skilled in the art from the following detailed description and appended claims.